Chapter 20: Lymphatic System and Immunity

Neutropenia (noo′-troh-PEE-nee-ah) is the condition of having insufficient levels of neutrophils in the blood. Predict the effect this condition will have on the body's ability to fight certain pathogens.

A deficiency in neutrophils puts one at great risk of bacterial infection, as neutrophils are one of the main types of cells responsible for killing bacteria.

Your friend argues that the third line of defense of the immune system is the most important and that the first and second are relatively unimportant. What do you tell him?

All three lines of defense rely on one another to function properly. If one line fails, the other two have great difficulty in protecting the body.

A patient presents with symptoms of a heart attack, andit is noted that she also has a fever. Her husband suggests that she must have an infection. What would you tell him?

Although it is possible that the patient has an infection, the fever could also be caused by inflammation due to tissue damage from a heart attack.

A virus develops a mutation that prevents the activation of TC cells. Predict the consequences of this mutation. What other components of the immune response would need to compensate for the lack of activated TC cells?

An inability to activate TC cells would decrease the ability of the body to fight off the viral infection, as TC cells would not lyse and kill infected cells. Essentially every other component of the immune response, particularly TH, NK, and B cells, would need to compensate for the lack of TC cells.

Mr. Jackson steps on a nail with his left foot and chooses not to seek medical treatment. Two weeks later, he presents to his physician with a complaint of painful masses in his groin on the left side. His physician notes that Mr. Jackson's inguinal lymph nodes are swollen. What has likely happened?

Bacteria or other pathogens were likely introduced into the wound, after which they traveled through the lymphatic vessels to the inguinal lymph nodes, where they were trapped.

Interstitial cystitis is characterized by erosion of the mucous membrane lining the urinary bladder. Predict the potential consequences of this condition.

Erosion of this mucous membrane compromises the first line of defense against pathogens and tissue damage. As a result, the urinary bladder is at higher risk of infection and damage from chemicals in urine.

A patient has undergone surgery for breast cancer in which the axillary lymph nodes and associated lymphatic vessels were removed. Predict the effects of removing lymph nodes and vessels.

Removal of the lymph nodes and vessels will increase the patient's risk of infection and also decrease the return of excess interstitial fluid back to the cardiovascular system, leading to edema.

A researcher is investigating a drug to prevent organ rejection; this drug selectively inhibits TH cells. How would this help to prevent rejection of a transplanted organ?

TH cells secrete interleukin-2, which is necessary for TC cells to become fully activated. If TH cells are inhibited, TC cells will do less damage to the cells of the donated organ.

A hypothetical poison acts on the cells of the kidney and induces a change in the genes for the self antigens displayed on their class I MHC molecules. Predict what might happen if this poison were administered to someone.

The change in the self antigens would likely cause the cells to be recognized by TC cells as foreign, and TC cells would attack and destroy the kidney cells.

What other effects would the drug from question 1 have on the immune system? Explain.

The drug would decrease many other components of the immune response, including innate and antibody-mediated immunity.

Blood work on the patient in question 3 shows an elevated level of neutrophils in her blood. What does this tell you about the possible cause of the fever? Explain.

The elevated level of neutrophils points to a bacterial infection as the possible cause of the fever, but this can't be determined definitively without more information.

A patient presents to the emergency room with a fever. What does the fever indicate?

The fever indicates that an inflammatory response is occurring in the patient's body.

A patient has a hypothetical disorder that prevents the development of memory cells. Predict the effects this disorder would have on the primary and secondary immune responses.

The lack of memory cells would effectively prevent the development of immunological memory, and a secondary immune response would be impossible. For this reason, every encounter with an antigen would initiate a primary immune response.

What would happen if cancer cells developed a mutation similar to that in question 1?

The result would be similar—TC cells would be unable to detect and destroy the cancer cells.

You are injured in a farming accident, and in the emergency room you are administered injections of both tetanus antitoxin, which contains antibodies to the tetanus toxin, and tetanus antigens. Which injection provided active immunity, and which passive? Explain.

The tetanus antitoxin provided passive immunity, as it contains pre- formed antibodies that will last only about 3 months. The tetanus anti- gens stimulates your immune system to produce its own antibodies, and so provides active immunity.

The disorder hypogammaglobulinemia is characterized by a decrease in the secretion of one or more classes of antibody. Predict the effect of decreased secretion of: a. IgA. b. IgG. c. IgG in a pregnant female. d. IgM.

a. Decreased secretion of IgA will decrease the effectiveness of surface barriers that release IgA with their secretions. b. IgG is the main antibody secreted in the secondary immune response. For this reason, a deficiency in IgG will prolong the duration and increase the severity of infection with many different types of pathogens c. A deficiency of IgG in a pregnant female puts both the mother and fetus at higher risk for developing prolonged and severe infections. It is particularly dangerous for the fetus, as maternal IgG is the only source of immunity before and immediately after birth. d. A decrease in IgM will prolong the primary immune response and potentially increase the severity of an infection, as IgM is generally the first antibody to arrive and contain an infection.

Predict the potential consequences of removing each of the following lymphoid organs: a. Spleen b. Thymus (in an adult) c. Thymus (in a newborn) d. Tonsils

a. Removal of the spleen will increase the risk of infection slightly. In addition, destruction of old erythrocytes will have to take place elsewhere, such as in the plasma and liver. b. Removal of the thymus in an adult will likely have few consequences, as T cell maturation has already taken place. c. Removal of the thymus in a newborn will stop T cell maturation, leading to severe dysfunction in the entire immune system. d. Removal of the tonsils will increase the risk of infection slightly, particularly around the oral and nasal cavities.

You are working in a nursing home, and Mrs. Jackson develops a fever. You prepare to call her doctor about the fever. Your co-worker suggests that it's not necessary to call the doctor, and that you should just administer aspirin to Mrs. Jackson to make her fever go away. What do you tell your co-worker?

fever is a sign that inflammation is occurring in the body. Although aspirin might make the fever decrease, it will not treat the underlying cause of the inflammation. For this reason, further examination is war- ranted any time a patient in such a setting develops an unexpected fever.